Flexible display device

ABSTRACT

A flexible display device includes a first non-bending area, a second non-bending area spaced apart from the first non-bending area, and a bending area between the first non-bending area and the second non-bending area; and a protective member on a surface of the flexible display panel, and including a first protective member overlapping the first non-bending area and a second protective member overlapping the second non-bending area, each of the first protective member and the second protective member including an inclined surface inclined with respect to the surface of the flexible display panel overlapping the flat area adjacent to the bending area, and the inclined surfaces do not physically contact each other in a bending state.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.15/785,198, filed Oct. 16, 2017, which is a continuation of U.S. patentapplication Ser. No. 15/335,061, filed Oct. 26, 2016, now U.S. Pat. No.9,811,120, which is a continuation-in-part of U.S. patent applicationSer. No. 14/298,792, filed Jun. 6, 2014, now U.S. Pat. No. 9,485,858,which claims priority to and the benefit of Korean Patent ApplicationNo. 10-2013-0146426, filed Nov. 28, 2013 in the Korean IntellectualProperty Office, the entire contents of all of which are incorporatedherein by reference.

BACKGROUND 1. Field of the Invention

The present disclosure relates to a display device. More particularly,the present disclosure relates to a flexible display device.

2. Description of the Related Art

In recent years, a flexible display device, which is formed of aflexible material, e.g., plastic, to maintain display performancethereof even though it is bent as if paper is folded, has been activelyresearched. The flexible display device has been spotlighted as a nextgeneration display device to replace various electronic equipments, suchas a portable computer, an electronic newspaper, a smart card, a printedmedia, etc.

The flexible display device includes a flexible display panel. Theflexible display panel includes a display area displaying an image and anon-display area surrounding the display area. The non-display areaincludes various circuit parts and line parts to apply image signals tothe display area and is positioned at the same plane as the displayarea.

To minimize the size of the non-display area in a plan view, theflexible display panel is curved in a direction opposite to a directionin which the image is displayed in the display area or the non-displayarea. Cracks occur in the line parts when the flexible display panel iscurved.

SUMMARY

The present disclosure provides a flexible display device capable ofreducing defects therein.

Embodiments of the inventive concept provide a flexible display devicecomprising a flexible display panel comprising a folding area and aperipheral area, and a first outer member on a surface of the flexibledisplay panel and comprising a first groove pattern extending in a firstdirection at the folding area, wherein the first groove patterncomprises, a first inclined portion having a first surface inclined tothe surface of the display panel, and a second inclined portion spacedapart from the first inclined portion in a second direction crossing thefirst direction, the second inclined portion having a second surfaceinclined to the surface of the display panel, wherein a width of thefirst groove pattern satisfies the FormulaW=F+(S1+S2)=π×Rand wherein W denotes the width of the first groove pattern, F denotes adistance between the first inclined portion and the second inclinedportion in the second direction, S1 denotes a width of the firstinclined portion in the second direction, S2 denotes a width of thesecond inclined portion in the second direction, π denotes a circularconstant, and R denotes a radius of curvature of the flexible displaypanel at the folding area.

In an exemplary embodiment, the first groove pattern exposes a portionof the surface of the display panel, and the distance between the firstinclined portion and the second inclined portion in the second directionis defined as width of the portion of the surface of the display panelin the second direction.

In an exemplary embodiment, the first groove pattern further comprises aflat portion parallel to the surface of the display panel and connectsto the first inclined portion and the second inclined portion, and thedistance between the first inclined portion and the second inclinedportion is defined as width of the flat portion in the second direction.

In an exemplary embodiment, the flat portion has a rough surface.

In an exemplary embodiment, the width of each of the first and secondinclined portions is about 1 μm to about 3 mm.

In an exemplary embodiment, each of the first and the second surfacesforms an obtuse angle with the surface of the display panel.

In an exemplary embodiment, at least one of the first and the secondsurfaces comprises a flat surface.

In an exemplary embodiment, at least one of the first and the secondsurfaces comprises a curved surface.

In an exemplary embodiment, at least one of the first and the secondsurfaces comprises a plurality of inclined surfaces arrayed in adirection parallel to the second direction.

In an exemplary embodiment, a respective angle between each of theplurality of the inclined surfaces and the surface of the display panelbecome greater as the inclined surfaces are closer to the peripheralarea in a plan view.

In an exemplary embodiment, the respective angle between each of theplurality of the inclined surfaces and the surface of the display panelis greater than about 90 degrees.

In an exemplary embodiment, each of the first and second inclinedportions comprises a step pattern comprising a plurality of steppedportions.

In an exemplary embodiment, the flexible display panel is folded at thefolding area around the first direction.

In an exemplary embodiment, the flexible display panel has a rectangularshape and the folding area extends along at least one edge of theflexible display panel.

In an exemplary embodiment, the flexible display panel is folded at anangle of about 180 degrees.

In an exemplary embodiment, the first groove pattern is at one or morepositions at the folding area as first groove patterns.

In an exemplary embodiment, further comprising a second outer member onanother surface of the flexible display panel and facing the first outermember, wherein the second outer member comprises a second groovepattern.

In an exemplary embodiment, the first groove pattern is at the foldingarea and the second groove pattern is at another folding area, and thefolding area and the other folding area are at different locations.

In an exemplary embodiment, the flexible display panel is folded indifferent directions at the folding area and the other folding area.

In an exemplary embodiment, the second groove pattern extends in adirection parallel to the first direction.

According to the above, the signal lines may be prevented from beingcracked even though the flexible display panel is folded.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other advantages of the present disclosure will becomereadily apparent by reference to the following detailed description whenconsidered in conjunction with the accompanying drawings wherein:

FIG. 1 is a perspective view showing a flexible display device accordingto an exemplary embodiment of the present disclosure;

FIG. 2 is an equivalent circuit diagram showing one pixel of theflexible display device shown in FIG. 1 ;

FIG. 3 is a plan view showing the one pixel of the flexible displaydevice shown in FIG. 2 ;

FIG. 4 is a cross-sectional view taken along a line I-I′ of FIG. 3 ;

FIG. 5 is a cross-sectional view taken along a line II-II′ of FIG. 3 ;

FIG. 6A is a cross-sectional view taken along a line A-A′ of FIG. 1 ;

FIG. 6B is a cross-sectional view showing the flexible display devicethat is folded;

FIG. 7 is a cross-sectional view showing a flexible display deviceaccording to another exemplary embodiment of the present disclosure;

FIG. 8 is a cross-sectional view showing a flexible display deviceaccording to another exemplary embodiment of the present disclosure;

FIG. 9 is a cross-sectional view showing a flexible display deviceaccording to another exemplary embodiment of the present disclosure;

FIGS. 10A-10B are views showing portions of cross-section of a flexibledisplay device according to an exemplary embodiment of the presentdisclosure;

FIG. 11 is a cross-sectional view showing a flexible display deviceaccording to an exemplary embodiment of the present disclosure;

FIG. 12 is a cross-sectional view showing a flexible display deviceaccording to an exemplary embodiment of the present disclosure; and

FIG. 13 is a cross-sectional view showing a flexible display device thatis folded according to another exemplary embodiment of the presentdisclosure.

DETAILED DESCRIPTION

The following description with reference to the accompanying drawings isprovided to assist in a comprehensive understanding of variousembodiments of the present disclosure as defined by the claims and theirequivalents. It includes various specific details to assist in thatunderstanding but these are to be regarded as merely exemplary.Accordingly, those of ordinary skill in the art will recognize thatvarious changes and modifications of the various embodiments describedherein can be made without departing from the scope and spirit of thepresent disclosure.

It will be further understood that the terms “includes” and/or“including”, when used in this specification, specify the presence ofstated features, integers, steps, operations, elements, and/orcomponents, but do not preclude the presence or addition of one or moreother features, integers, steps, operations, elements, components,and/or groups thereof. It will be understood that when an element orlayer is referred to as being “on”, “connected to” or “coupled to”another element or layer, it can be directly on, connected or coupled tothe other element or layer or intervening elements or layers may bepresent. In contrast, when an element is referred to as being “directlyon,” “directly connected to” or “directly coupled to” another element orlayer, there are no intervening elements or layers present.

Like numbers refer to like elements throughout. In the drawings, thethickness of layers, films, and regions are exaggerated for clarity. Asused herein, the term “and/or” includes any and all combinations of oneor more of the associated listed items. The use of the terms first,second, etc. do not denote any order or importance, but rather the termsfirst, second, etc. are used to distinguish one element from another.Thus, a first element, component, region, layer or section discussedbelow could be termed a second element, component, region, layer orsection without departing from the teachings of the present invention.It is to be understood that the singular forms “a,” “an,” and “the”include plural referents unless the context clearly dictates otherwise.

Hereinafter, the present invention will be explained in detail withreference to the accompanying drawings.

FIG. 1 is a perspective view showing a flexible display device accordingto an exemplary embodiment of the present disclosure.

Referring to FIG. 1 , the flexible display device includes a flexibledisplay panel DP, a first outer member P1 disposed on one surface of theflexible display panel DP, and a second outer member P2 disposed on theother surface of the flexible display panel DP.

For the convenience of explanation, a direction in which an image isdisplayed in the display device is referred to as an upper direction anda direction opposite to the upper direction is referred to as a lowerdirection, but they should not be limited thereto or thereby.

The flexible display panel DP displays the image. The flexible displaypanel DP may be an organic light emitting display panel or a plasmadisplay panel, but it should not be limited thereto or thereby. That is,the flexible display panel DP may be a liquid crystal display panel, anelectrowetting display panel, an electrophoretic display panel, or amicroelectromechanical system (MEMS) display panel. In the presentexemplary embodiment, the organic light emitting display panel will bedescribed as the flexible display panel DP as a representative example.

The flexible display panel DP includes a display area DA in which theimage is displayed and a non-display area NDA disposed at a positionadjacent to at least one side of the display area DA.

The flexible display panel DP includes a flexible substrate, signallines disposed on the flexible substrate, and pixels PX electricallyconnected to the signal lines. The pixels PX generate the image on thebasis of the signals provided from the signal lines.

The flexible display panel DP has a rectangular shape with two pairs ofsides and each pair includes two sides substantially parallel to eachother. The sides of one pair of the two pairs are longer than the sidesof the other pair of the two pairs. In the present exemplary embodiment,the flexible display panel DP has the rectangular shape defined by apair of long sides and a pair of short sides, a direction in which theshort sides extend is referred to as a first direction D1, and adirection in which the long sides extend is referred to as a seconddirection D2.

The flexible display panel DP may be curved or wrapped to have a curvedsurface, or folded in a specific area thereof. The flexible displaypanel DP includes a folding area FA and a peripheral area SA in a planview defined by the first direction D1 and the second direction D2. Thefolding areas FA correspond to areas each in which the flexible displaypanel DP is folded. The peripheral areas SA are disposed adjacent to thefolding area FA.

FIG. 1 shows the flexible display panel DP including two folding areasFA and three peripheral areas SA, but the number of the folding areas FAand the peripheral areas SA should not be limited thereto or thereby.That is, at least one folding area FA may be provided along at least oneedge of the flexible display panel DP. In addition, the folding area FAmay be provided in a center portion of the flexible display panel DPrather than the edge of the flexible display panel DP if necessary.

The folding areas FA and the peripheral areas SA may include a portionof the pixels PX. The folding areas FA and the peripheral areas SA maydisplay the image regardless of the areas. The peripheral areas SA maybe flat or slightly curved.

The first outer member P1 is disposed on the surface of the flexibledisplay panel DP. In the present exemplary embodiment, the first outermember P1 is disposed under the flexible display panel DP. The firstouter member P1 may include at least one of a polarizing plate and aprotective member. In addition, two or more first outer members P1 maybe disposed on the surface of the flexible display panel DP. The firstouter member P1 is formed of a flexible plastic.

The first outer member P1 includes a groove pattern GP formed at aposition corresponding to the folding area FA. FIG. 1 shows two groovepatterns GP respectively corresponding to two folding areas FA, but thenumber of the groove patterns GP should not be limited to two. That is,the groove pattern GP may be provided in a plural number and the groovepatterns GP may be disposed to respectively correspond to the foldingareas FA. In the case that the plural groove patterns GP are provided,the groove patterns GP may have the same shape or different shapes, andthe groove patterns GP may have the same width or different widths.

Although not shown in figures, the flexible display device may furtherinclude an adhesive member (not shown) disposed between the flexibledisplay panel DP and the first outer member P1 to attach the flexibledisplay panel DP and the first outer member P1.

The second outer member P2 is disposed on the other surface of theflexible display panel DP to face the first outer member P1. In thepresent exemplary embodiment, the second outer member P2 is disposed onthe flexible display panel DP. The second outer member P2 may include atleast one of a polarizing plate, a touch screen, and a protectivemember. In addition, two or more second outer members P2 may be disposedon the other surface of the flexible display panel DP. The second outermember P2 may further include a functional coating layer, e.g., ananti-fingerprint coating layer, an anti-reflection coating layer, etc.The second outer member P2 may be formed of a flexible plastic material.

Although not shown in figures, the flexible display device may furtherinclude an adhesive member (not shown) disposed between the flexibledisplay panel DP and the second outer member P2 to attach the flexibledisplay panel DP and the second outer member P2.

Hereinafter, the flexible organic light emitting display panel will bedescribed in detail with reference to FIGS. 2 to 5 . For the convenienceof explanation, only one pixel PX will be described as a representativeexample.

FIG. 2 is an equivalent circuit diagram showing one pixel of theflexible display device shown in FIG. 1 , FIG. 3 is a plan view showingthe one pixel of the flexible display device shown in FIG. 2 , FIG. 4 isa cross-sectional view taken along a line I-I′ of FIG. 3 , and FIG. 5 isa cross-sectional view taken along a line II-II′ of FIG. 3 .

The flexible display panel DP includes a base substrate SUB1 that isflexible, the signal lines disposed on the base substrate SUB1, thepixel PX connected to the signal lines, and a sealing substrate SUB2disposed on the signal lines and the pixel PX.

The base substrate SUB1 is formed of a plastic material with highthermal resistance and high durability, such as polyethyleneterephthalate (PET), polyethylene naphthalate (PEN), polycarbonate (PC),polyarylate (PAR), polyether imide (PEI), polyether sulfone (PES),polyimide (PI), etc., but the material for the base substrate SUB1should not be limited thereto or thereby.

The flexible display panel DP may further include a barrier layer (notshown) disposed on the base substrate SUB1. The barrier layer (notshown) includes at least one of an organic layer and an inorganic layer.The barrier layer (not shown) prevents foreign substances from enteringinto the display area DA after passing through the base substrate SUB1.

The signal lines are disposed on the base substrate SUB1 and include agate line GL extending in the first direction D1, a data line DLextending in the second direction D2 crossing the first direction D1,and a power source line KL receiving a first voltage ELVDD.

The pixel PX is connected to the gate line GL and the data line DL andincludes a first thin film transistor TFT1, a second thin filmtransistor TFT2, a capacitor Cap, and an organic light emitting diodeOLED. The first thin film transistor TFT1, the capacitor Cap, and thesecond thin film transistor TFT2 form a circuit part to control theorganic light emitting diode OLED.

The first thin film transistor TFT1 outputs a data signal applied to thedata line DL in response to a gate signal applied to the gate line GL.The second thin film transistor TFT2 controls a driving current flowingthrough the organic light emitting diode OLED in response to an amountof electric charge charged in the capacitor Cap. The pixel PX receivesthe first voltage ELVDD and a second voltage ELVSS having a differentvoltage level from that of the first voltage ELVDD.

Hereinafter, a structure of the flexible display panel DP will bedescribed in detail.

A semiconductor pattern SM1 (hereinafter, referred to as a firstsemiconductor pattern) of the first thin film transistor TFT1 and asemiconductor pattern SM2 (hereinafter, referred to as a secondsemiconductor patter) of the second thin film transistor TFT2 aredisposed on the base substrate SUB1. A first insulating layer 12 isdisposed on the base substrate SUB1 to cover the first semiconductorpattern SM1 and the second semiconductor pattern SM2. The firstinsulating layer 12 includes an organic and/or inorganic layer. Thefirst insulating layer 12 may include a plurality of thin film layers.

A control electrode GE1 (hereinafter, referred to as a first controlelectrode) of the first thin film transistor TFT1 and a controlelectrode GE2 (hereinafter, referred to as a second control electrode)of the second thin film transistor TFT2 are disposed on the firstinsulating layer 12. A first electrode CE1 of the capacitor Cap isdisposed on the first insulating layer 12.

A second insulating layer 14 is disposed on the first insulating layer12 to cover the first control electrode GE1, the second controlelectrode GE2, and the first electrode CE1. The second insulating layer14 includes an organic and/or inorganic layer. The second insulatinglayer 14 may include a plurality of thin film layers.

An input electrode SE1 (hereinafter, referred to as a first inputelectrode) and an output electrode DE1 (hereinafter, referred to as afirst output electrode) of the first thin film transistor TFT1 aredisposed on the second insulating layer 14. An input electrode SE2(hereinafter, referred to as a second input electrode) and an outputelectrode DE2 (hereinafter, referred to as a second output electrode) ofthe second thin film transistor TFT2 are disposed on the secondinsulating layer 14. The second input electrode SE2 is connected to thepower source line KL. A second electrode CE2 of the capacitor Cap isfurther disposed on the second insulating layer 14.

The first input electrode SE and the first output electrode DE1 areconnected to the first semiconductor pattern SM1 respectively throughfirst and second contact holes CH1 and CH2 formed through the firstinsulating layer 12 and the second insulating layer 14. The first outputelectrode DE1 is connected to the first electrode CE1 through a thirdcontact hole CH3 formed through the second insulating layer 14. Thesecond input electrode SE2 and the second output electrode DE2 areconnected to the second semiconductor pattern SM2 respectively throughfourth and fifth contact holes CH4 and CH5 formed through the firstinsulating layer 12 and the second insulating layer 14. Meanwhile,according to another embodiment, each of the first and second thin filmtransistors TFT1 and TFT2 may have a bottom gate structure.

A third insulating layer 16 is disposed on the second insulating layer14 to cover the first input electrode SE1, the first output electrodeDE1, the second input electrode SE2, and the second output electrodeDE2. The third insulating layer 16 includes an organic and/or inorganiclayer. The third insulating layer 16 may include a plurality of thinfilm layers.

A pixel definition layer PDL and the organic light emitting diode OLEDare disposed on the third insulating layer 16. The organic lightemitting diode OLED includes an anode AE, a first common layer CL1, anorganic light emitting layer EML, a second common layer CL2, and acathode CE, which are sequentially stacked one on another. The anode AEis connected to the second output electrode DE2 through a sixth contacthole CH6 formed through the third insulating layer 16. Positions of theanode AE and the cathode CE may be changed with respect to each other inaccordance with a direction to which the organic light emitting diodeOLED emits the light.

The anode AE is disposed on the third insulating layer 16 and exposedthrough an opening OP of the pixel definition layer PDL. The firstcommon layer CL1 is disposed on the anode AE. The first common layer CL1is disposed not only in the light emitting area corresponding to theopening OP but also in the non-light emitting area. That is, the firstcommon layer CL1 is disposed over the entire surface of the basesubstrate SUB1. The first common layer CL1 includes a hole injectionlayer. The first common layer CL1 may further include a hole transportlayer.

The organic light emitting layer EML is disposed on the first commonlayer CL1. The organic light emitting layer EML is disposed only in thearea corresponding to the opening OP. The second common layer CL2 isdisposed on the organic light emitting layer EML. Similar to the firstcommon layer CL1, the second common layer CL2 is disposed over theentire surface of the base substrate SUB1. The second common layer CL2includes an electron injection layer. The second common layer CL2 mayfurther include an electron transport layer. The cathode CE is disposedon the second common layer CL2. The cathode CE is disposed over theentire surface of the base substrate SUB1.

A fourth insulating layer 18 is disposed on the cathode CE. The fourthinsulating layer 18 includes an organic and/or inorganic layer. Thefourth insulating layer 18 may include a plurality of thin film layers.The sealing substrate SUB2 is disposed on the fourth insulating layer18. The sealing substrate SUB2 may be a flexible plastic substrate. Thesealing substrate SUB2 may be replaced with a sealing thin film layer.

FIG. 6A is a cross-sectional view taken along a line A-A of FIG. 1 .

FIG. 6B is a cross-sectional view showing the flexible display devicethat is folded.

Hereinafter, the flexible display panel according to the exemplaryembodiment of the present disclosure will be described in detail withreference to FIGS. 6A-6B. For the convenience of explanation, the firstouter member P1 will be mainly described.

Referring to FIG. 6A, the first outer member P1 is disposed under theflexible display panel DP and includes the groove pattern GP formed atthe position corresponding to the folding area FA.

The groove pattern GP includes a first inclined portion SL1 and a secondinclined portion SL2. The first inclined portion SL1 is spaced apartfrom the second inclined portion SL2 in the first direction D1.

The first inclined portion SL1 includes a first surface IS1. The firstsurface IS1 is inclined at a first inclined angle 61 with respect to asurface of the flexible display panel DP. The first inclined angle 61may be equal to or greater than about 90 degrees. In the presentexemplary embodiment, the first inclined angle 61 may be an obtuseangle.

The second inclined portion SL2 includes a second surface IS2. Thesecond surface IS2 is inclined at a second inclined angle 62 withrespect to the surface of the flexible display panel DP. The secondinclined angle 62 may be equal to or greater than about 90 degrees. Inthe present exemplary embodiment, the second inclined angle 62 may be anobtuse angle.

The groove pattern GP may be formed by removing at least a portion ofthe first outer member P1. The first surface IS1, the second surfaceIS2, and a flat surface FS are exposed by removing the portion of thefirst outer member P1. Accordingly, the groove pattern GP may have ashape defined by the first surface IS1, the second surface IS2, and theflat surface FS.

The flat surface FS may be a surface disposed between the first surfaceIS1 and the second surface IS2 to connect the first surface IS1 and thesecond surface IS2. The flat surface FS may be substantially parallel tothe flexible display panel DP, and each of the first surface IS1 and thesecond surface IS2 may be inclined with respect to the flat surface FS.

The groove pattern GP has a width W in the first direction D1. The widthW of the groove pattern GP may be equal to or greater than a width inthe first direction D1 of the folding area FA. The width W of the groovepattern GP satisfies the following Formula 1.W=F+(S1+S2)=π×R  Formula 1

In Formula 1, “F” denotes a separation distance (hereinafter, referredto as a “separation width) in the first direction D1 between the firstinclined portion SL1 and the second inclined portion SL2, “S1” denotes awidth (hereinafter, referred to as a “first width”) in the firstdirection D1 of the first inclined portion SL1, “S2” denotes a width(hereinafter, referred to as a “second width”) in the first direction D1of the second inclined portion SL2, “π” denotes a circular constant, and“R” denotes a radius of curvature in the folding area FA.

The width W of the groove pattern GP is equal to a sum of the separationwidth F, the first width S1, and the second width S2. In the presentexemplary embodiment, each of the first and second widths S1 and S2 maybe equal to or greater than about 1 μm and equal to or smaller thanabout 3 mm.

In the present exemplary embodiment, the first inclined portion SL1 andthe second inclined portion SL2 may expose at least a portion of thesurface of the flexible display panel DP. The flat surface FS maycorrespond to the exposed portion of the surface of the flexible displaypanel DP. Accordingly, the separation width F may correspond to a widthin the first direction D1 of the exposed portion of the surface of theflexible display panel DP.

The width W of the groove pattern GP may be differently designeddepending on the radius of curvature R. In addition, the separationwidth F, the first width S1, and the second width S2 may be differentlydesigned depending on the radius of curvature R.

The flexible display device according to the present exemplaryembodiment may be folded at about 180 degrees with respect to a foldingaxis extending parallel to the second direction D2, and thus theperipheral areas SA disposed adjacent to opposite sides of the foldingarea FA may be overlapped with each other. A direction in which thegroove pattern GP extends may be substantially parallel to the foldingaxis of the flexible display device. In the present exemplaryembodiment, the folding axis may penetrate through a center of a circledefined by the radius of curvature R.

When an external force is applied to the flexible display deviceaccording to the present exemplary embodiment in order to fold theflexible display device, the second outer member P2 disposed at an outerside of the folding area FA is applied with a tensile stress and thefirst outer member P1 disposed at an inner side of the folding area FAis applied with a compression stress. In this case, a neutral plane NP,in which no tensile stress or compression stress occurs, exists betweenthe first outer member P1 and the second outer member P2. When theneutral plane NP is disposed on the flexible display panel DP, thestress applied to the flexible display panel DP is reduced, and thus theflexible display panel DP may be prevented from being damaged whilebeing folded. Accordingly, the groove pattern GP is formed in thefolding area FA of the first outer member P1 in order to remove orreduce the compression stress applied to the first outer member P1. Whenthe flexible display device is folded, the groove pattern GP is locatedat a position at which the compression stress becomes maximum in thefolding area FA. Particularly, since the neutral plane NP graduallymoves to the flexible display panel DP from the first outer member P1due to the groove pattern GP formed in the folding area FA, the signallines may be prevented from being cracked even though the flexibledisplay panel DP is folded.

FIG. 7 is a cross-sectional view showing a flexible display deviceaccording to another exemplary embodiment of the present disclosure. Forthe convenience of explanation, the same elements will be assigned thesame reference numerals, and thus detailed descriptions of the sameelements will be omitted.

Referring to FIG. 7 , the first outer member P1 is disposed under theflexible display panel DP and includes a groove pattern GP formed in thefolding area FA.

The groove pattern GP includes a flat surface FS and a first inclinedportion SL1-1 and a second inclined portion SL2-1 respectively connectedto the flat surface FS and symmetrical with each other about the flatsurface FS. The flat surface FS is defined by removing a portion of thefirst outer member P1 or by minimizing a thickness of the first outermember P1.

The first and second inclined portions SL1-1 and SL2-1 may respectivelyinclude first and second surfaces IS1-1 and IS2-1, each including aplurality of inclined surfaces. The inclined portions may be arranged inthe first direction D1.

The first inclined portion SL1-1 includes the inclined surfaces thatrespectively form first, second, and third angles θa, θb, and θc withthe flat surface FS. The first, second, and third angles θa, θb, and θcare equal to or greater than about 90 degrees. The inclined surfacesbecome farther from the flat surface FS as they go to the thirddirection D3 in which the inclined portions SL become farther from theflexible display panel DP. That is, the first, second, and third anglesθa, θb, and θc satisfy the following Formula 2.90°≤θa≤θb≤θc≤180°  Formula 2

Here, the first surface IS1-1 includes three inclined surfaces that formthe first, second, and third angles θa, θb, and θc with the flat surfaceFS, but it should not be limited thereto or thereby. That is, the firstsurface IS1-1 may include at least two inclined surfaces. Meanwhile, thefirst surface IS1-1 may include a curved surface configured to include aplurality of inclined surfaces at at least a portion of the curvedsurface.

Meanwhile, the second surface IS2-1 may include a plurality of inclinedsurfaces arranged in the first direction, and angles between theinclined surfaces and the flat surface FS may be independently designedfrom the first surface IS1-1.

Accordingly, the first surface IS1-1 and the second surface IS2-1 mayhave shapes symmetrical with or different from each other. As anotherway, one surface of the first surface IS1-1 and the second surface IS2-1may include a plurality of inclined surfaces, and the other surface ofthe first surface IS1-1 and the second surface IS2-1 may include asingle inclined surface. The groove pattern according to the presentexemplary embodiment may have various shapes and should not be limitedto a specific shape.

A width W of the groove pattern GP is equal to a sum of a separationwidth F corresponding to a width of the flat surface FS, a first widthS1 corresponding to a width of the first inclined portion, and a secondwidth S2 corresponding to a width of the second inclined portion. In thepresent exemplary embodiment, each of the first width S1 and the secondwidth S2 may be about 1 μm to about 3 mm. The width W of the groovepattern GP may be differently designed depending on the radius ofcurvature R in the folding area FA when the flexible display device isfolded. In addition, the separation width F, the first width S1 and thesecond width S2 may be differently designed in accordance with theradius of curvature R.

FIG. 8 is a cross-sectional view showing a flexible display deviceaccording to another exemplary embodiment of the present disclosure.

Referring to FIG. 8 , the first outer member P1 is disposed under theflexible display panel DP and includes a groove pattern GP formed in thefolding area FA.

The flat surface FS is defined by removing a portion of the first outermember P1 or by minimizing a thickness of the first outer member P1.

The groove pattern GP according to the present exemplary embodiment maybe defined by a first surface IS1-2, a second surface IS2-2, and a flatsurface FS. Each of the first surface IS1-2 and the second surface IS2-2may include a plurality of stepped portions SP. A width W of the groovepattern GP satisfies the following Formula 3.W=F+(S1+S2)=F+n×(SP)=π×R  Formula 3

In Formula 3, “F” denotes a width of the flat surface FS correspondingto the above-mentioned separation width F, “S1” denotes a width(hereinafter, referred to as a “first width”) of the first inclinedportion, S2 denotes a width (hereinafter, referred to as a “secondwidth”) of the second inclined portion, “n” denotes the number of thestepped portions, “SP” denotes a width (hereinafter, referred to as a“third width”) of the stepped portion, “T” denotes a circular constant,and “R” denotes a radius of curvature in the folding area FA.

The width W of the groove pattern GP is equal to a sum of the separationwidth F, the first width S1, and the second width S2. In the presentexemplary embodiment, each of the first and second widths S1 and S2 maybe about 1 μm to about 3 mm.

Each of the first width S1 and the second width S2 may be equal to a sumof widths in the first direction D1 of the stepped portions SP formingthe first and second surfaces IS1-2 and IS2-2. Accordingly, the thirdwidth SP may correspond to the width of any one of the stepped portionsand may be equal to or greater than about 0.01 μm and smaller than about3 mm.

In the present exemplary embodiment, the stepped portions have the samewidth as each other, but they should not be limited thereto or thereby.That is, the stepped portions may have different widths from each other,and in this case, the sum of the first and second widths S1 and S2 maybe a sum of the widths of the stepped portions.

The width W of the groove pattern GP may have various values dependingon the radius of curvature R. In addition, each of the separation widthF, the first width S1, and the second width S2 may be differentlydesigned in accordance with the radius of curvature R.

FIG. 9 is a cross-sectional view showing a flexible display deviceaccording to an exemplary embodiment of the present disclosure. FIGS.10A-10B are views showing portions of cross-section of a flexibledisplay device according to an exemplary embodiment of the presentdisclosure. For the convenience of explanation, FIG. 9 shows an areacorresponding to that shown in FIG. 6A and FIGS. 10A-10B are microscopepictures showing areas each in which the groove pattern is disposed.

Hereinafter, the flexible display device will be described in detailwith reference to FIGS. 9 and 10A-10B. In FIGS. 9 and 10A-10B, the samereference numerals denote the same elements in FIGS. 1 to 6B, and thusdetailed descriptions of the same elements will be omitted.

Referring to FIG. 9 , a groove pattern GP-1 includes a first inclinedportion SL1, a second inclined portion SL2, and a flat surface portionFL. The flat surface portion FL is disposed between the first inclinedportion SL1 and the second inclined portion SL2 to connect the firstinclined portion SL1 and the second inclined portion SL2.

The flat surface portion FL makes contact with a surface of the flexibledisplay panel DP. The flat surface portion FL may be substantiallyparallel to the surface of the flexible display panel DP. The flatsurface portion FL may have a thickness smaller than a thickness of eachof the first and second inclined portions SL1 and SL2.

The flat surface portion FL may be a portion of the first outer memberP1. For instance, in a case that the first outer member P1 includes abase substrate and an adhesive member adhering the base substrate andthe flexible display panel DP, the flat surface portion FL may serve asthe adhesive member. As another example, the flat surface portion FL maybe the adhesive member and a portion of the base substrate. In thiscase, the flat surface portion FL, the first inclined portion SL1, andthe second inclined portion SL2 may have an integral shape.

The groove pattern GP-1 may have a shape defined by the first inclinedsurface IS1, the second inclined surface IS2, and the flat surface FS.In this case, the flat surface FS may correspond to a surface of theflat surface portion FL. Accordingly, the separation width F in Formula1 may correspond to a width in the first direction D1 of the flatsurface portion FL.

As shown in FIGS. 9 and 10A-10B, the flat surface FS may have variousshapes. For instance, the flat surface FS may be a substantially flatsurface as shown in FIG. 9 . As another example, the flat surface FS mayhave a rough surface as shown in FIGS. 10A-10B.

In the flexible display device according to the present exemplaryembodiment, the groove pattern GP-1 may be defined by removing only aportion of the first outer member P1. The flat surface portion FL mayserve as a protective layer covering the surface of the flexible displaypanel DP. Thus, the groove pattern GP-1 may be stably formed withoutdamaging the flexible display panel DP.

FIG. 11 is a cross-sectional view showing a flexible display deviceaccording to an exemplary embodiment of the present disclosure.

Referring to FIG. 11 , the second outer member P2 is disposed on theflexible display panel DP and includes a groove pattern GP formed in thefolding area FA. The groove pattern GP includes a first inclined portionSL1 and a second inclined portion SL2. The groove pattern GP has a shapedefined by a flat surface FS, a first surface of the first inclinedportion SL1, and a second surface of the second inclined portion SL2.Accordingly, the groove pattern GP may have a plurality of steppedportions.

The groove pattern GP includes the flat surface FS and inclined portionsSL connected to the flat surface FS and symmetrical with each otherabout the flat surface FS.

The flat surface FS is defined by removing a portion of the second outermember P2 or by minimizing a thickness of the second outer member P2.

The width W of the groove pattern GP is equal to a sum of the width F ofthe flat surface FS and the widths S1 and S2 of the first and secondinclined portions SL1 and SL2. The width W of the groove pattern GP maybe differently designed depending on the radius of curvature R. Inaddition, the width F of the flat surface FS and the first and secondwidths S1 and S2 of the first and second inclined portions SL1 and SL2may have various values in accordance with the radius of curvature R.

Here, when an external force is applied to the flexible display devicein order to fold the flexible display device in the direction oppositeto the third direction D3, the first outer member P1 disposed at anouter side of the folding area FA is applied with a tensile stress andthe second outer member P2 disposed at an inner side of the folding areaFA is applied with a compression stress. Accordingly, the groove patternGP is formed in the folding area FA of the second outer member P2 inorder to remove or reduce the compression stress applied to the secondouter member P2. When the flexible display device is folded, the groovepattern GP is located at a position at which the compression stressbecomes maximum in the folding area FA.

FIG. 12 is a cross-sectional view showing a flexible display deviceaccording to another exemplary embodiment of the present disclosure.

Referring to FIG. 12 , the first outer member P1 is disposed under theflexible display panel DP and includes a first groove pattern GP1 formedin the folding area FA. The second outer member P2 is disposed on theflexible display panel DP and includes a second groove pattern GP2formed in the folding area FA.

The first groove pattern GP1 includes a first lower inclined portionSL1-A and a second lower inclined portion SL2-A. The first groovepattern GP1 has a shape defined by a first surface of the first lowerinclined portion SL1-A, a second surface of the second lower inclinedportion SL2-A, and a first flat surface FS1.

The first flat surface FS1 is defined by removing a portion of the firstouter member P1 or by minimizing a thickness of the first outer memberP1. In this case, the first flat surface FS1 may be defined by aportion, which is exposed by the first lower inclined portion SL1-A andthe second lower inclined portion SL2-A, of the surface of the flexibledisplay panel DP.

The second groove pattern GP2 includes a first upper inclined portionSL1-B and a second upper inclined portion SL2-B. The second groovepattern GP2 has a shape defined by a first surface of the first upperinclined portion SL1-B, a second surface of the second upper inclinedportion SL2-B, and a second flat surface FS2.

The second flat surface FS2 is defined by removing a portion of thesecond outer member P2 or by minimizing a thickness of the second outermember P2. In this case, the second flat surface FS2 may be defined by aportion, which is exposed by the first upper inclined portion SL1-B andthe second upper inclined portion SL2-B, of the other surface of theflexible display panel DP.

Meanwhile, according to the present exemplary embodiment, the secondgroove pattern GP2 may be disposed in an area overlapped with the firstgroove pattern GP1 when viewed in a plan view. Accordingly, the firstflat surface FS1 and the second flat surface FS2 may respectivelycorrespond to portions, which face each other, of the surface and theother surface of the flexible display panel DP. However, according toanother embodiment, the second groove pattern GP2 may be disposed in anarea not overlapped with the first groove pattern GP1 when viewed in aplan view.

Each of the first lower inclined portion SL1-A, the second lowerinclined portion SL2-A, the first upper inclined portion SL1-B, and thesecond upper inclined portion SL2-B may have a step pattern defined bystepped portions. Each of the first lower inclined portion SL1-A, thesecond lower inclined portion SL2-A, the first upper inclined portionSL1-B, and the second upper inclined portion SL2-B may have variousshapes, but it should not be limited thereto or thereby.

As described above, since the first groove pattern GP1 and the secondgroove pattern GP2 are respectively formed in the first outer member P1and the second outer member P2 in the folding area FA, a neutral planeexists in the flexible display panel DP. Therefore, although theflexible display device is folded in the third direction D3 or thedirection opposite to the third direction D3, the stress applied to theflexible display panel DP is minimized. Thus, the flexible display panelDP may be prevented from being damaged.

FIG. 13 is a cross-sectional view showing a flexible display device thatis folded according to another exemplary embodiment of the presentdisclosure.

The flexible display device shown in FIG. 13 includes two folding areasFA1 and FA2 and four peripheral areas SA adjacent to the folding areasFA1 and FA2.

The flexible display device includes a flexible display panel DP, afirst outer member P1 disposed on one surface of the flexible displaypanel DP, and a second outer member P2 disposed on the other surface ofthe flexible display panel DP.

The first outer member P1 is disposed under the flexible display panelDP and includes a first groove pattern GP1 formed in the first foldingarea FA1. The second outer member P2 is disposed on the flexible displaypanel DP and includes a second groove pattern GP2 formed in the secondfolding area FA2.

The flexible display panel DP is folded in the third direction D3 in thefirst folding area FA1 and folded in the direction opposite to the thirddirection D3 in the second folding area FA2. Here, the flexible displaypanel DP is folded at about 180 degrees, but it should not be limitedthereto or thereby. In addition, the first groove pattern GP1 and thesecond groove pattern GP2 have the same shape as shown in FIG. 11 , butthe first groove pattern GP1 and the second groove pattern GP2 may havedifferent shapes according to embodiments. Further, the width of thefirst groove pattern GP1 may be different from the width of the secondgroove pattern GP2, and thus the folding degree of the flexible displaypanel DP may be varied.

Although the exemplary embodiments of the present invention have beendescribed, it is understood that the present invention should not belimited to these exemplary embodiments but various changes andmodifications can be made by one ordinary skilled in the art within thespirit and scope of the present invention as hereinafter claimed.

What is claimed is:
 1. A flexible display device comprising: a flexibledisplay panel comprising a first non-bending area, a second non-bendingarea spaced apart from the first non-bending area, and a bending areabetween the first non-bending area and the second non-bending area; anda protective member on a surface of the flexible display panel, andcomprising a first protective member overlapping the first non-bendingarea and a second protective member overlapping the second non-bendingarea; wherein each of the first protective member and the secondprotective member comprises an inclined portion inclined with respect tothe surface of the flexible display panel, a portion overlapping thebending area of the surface of the flexible display panel is exposedbetween the inclined portions, the bending area is bent along a virtualbending axis in a bending state, and a space defined by the portion andthe inclined portions spaced apart from each other has a trapezoidalshape in a non-bending state, and respective inclined surfaces of theinclined portions do not physically contact each other in the bendingstate.
 2. The flexible display device of claim 1, wherein each of theinclined portions is inclined at an acute angle with respect to thesurface of the flexible display panel.
 3. The flexible display device ofclaim 1, wherein the first protective member and the second protectivemember are each a single layer.
 4. The flexible display device of claim1, further comprising an adhesive member between the flexible displaypanel and the protective member to bond the flexible display panel andthe protective member.
 5. The flexible display device of claim 1,further comprising a touch screen on another surface of the flexibledisplay panel facing away from the surface of the flexible displaypanel.
 6. The flexible display device of claim 5, further comprising anadhesive member between the touch screen and the flexible display panelto bond the touch screen and the flexible display panel.
 7. The flexibledisplay device of claim 5, further comprising a polarizing plate on thetouch screen.
 8. A flexible display device comprising: a flexibledisplay panel comprising a bending area and non-bending area adjacent tothe bending area; and a protective member on a surface of the flexibledisplay panel, and comprising a first protective member and a secondprotective member; wherein the first protective member and secondprotective member are spaced apart from each other and expose a portionof the bending area; wherein each of the first protective member and thesecond protective member comprises an inclined portion inclined withrespect to the surface of the flexible display panel overlapping thenon-bending area adjacent to the bending area, the bending area is bentalong a virtual bending axis in a bending state, and an angle betweenthe portion and the respective inclined portion is an obtuse angle in anon-bending state, and respective inclined surfaces of the inclinedportions do not physically contact each other in the bending state. 9.The flexible display device of claim 8, wherein the first protectivemember and the second protective member are each a single layer.
 10. Theflexible display device of claim 8, further comprising an adhesivemember between the flexible display panel and the protective member tobond the flexible display panel and the protective member.
 11. Theflexible display device of claim 8, further comprising a touch screen onanother surface of the flexible display panel facing away from thesurface of the flexible display panel, and an adhesive member betweenthe touch screen and the flexible display panel to bond the touch screenand the flexible display panel.
 12. The flexible display device of claim11, further comprising a polarizing plate on the touch screen.
 13. Aflexible display device comprising: a flexible display panel comprisinga bending area and a flat area adjacent to the bending area; and aprotective member on a surface of the flexible display panel, andcomprising a first protective member and a second protective member;wherein the first protective member and second protective member arespaced apart from each other and expose a portion of the bending area,wherein each of the first protective member and the second protectivemember comprises an inclined surface inclined with respect to thesurface of the flexible display panel overlapping the flat area adjacentto the bending area, and wherein the inclined surfaces do not physicallycontact each other in a bending state.
 14. The flexible display deviceof claim 13, wherein the first protective member and the secondprotective member are each a single layer.
 15. The flexible displaydevice of claim 13, further comprising an adhesive member between theflexible display panel and the protective member to bond the flexibledisplay panel and the protective member.
 16. The flexible display deviceof claim 13, further comprising a touch screen on another surface of theflexible display panel facing away from the surface of the flexibledisplay panel, and an adhesive member between the touch screen and theflexible display panel to bond the touch screen and the flexible displaypanel.
 17. The flexible display device of claim 16, further comprising apolarizing plate on the touch screen.